Morning Stiffness Assessment Scale for Patients With Rheumatoid Arthritis: Turkish Adaptation and Validity and Reliability.

Participants were recruited via convenience sampling through social media and email, which may introduce selection bias and overrepresent individuals with internet access and higher digital literacy. Rheumatoid arthritis diagnosis was based on self-reported information rather than official medical records, which may introduce reporting bias. The confirmatory factor analysis was conducted on a relatively modest sample size of 150, which may limit the stability of parameter estimates and generalizability. Test-retest reliability was assessed in a small subsample of 30 participants, and the very high correlation coefficients may partly reflect recall bias. Exploratory factor analysis was not conducted, so potential culture-specific variations in factor structure were not explored. Item 2, which measures duration, had relatively lower psychometric performance, possibly reflecting participants' subjective difficulty in accurately quantifying time.

The authors declare no conflicts of interest and report no funding.

Do not assume this scale has been validated for use in English-speaking populations or outside Turkey. The study only tested the Turkish adaptation, and cross-cultural validation in other languages and settings has not been reported.